1. Field of the Invention
The present invention relates to watercraft, particularly to canoes and to a method to construct a canoe out of a single sheet of aluminum and to eliminate the need for a keel in the design and associated rivets, particularly rivets below the waterline.
2. Prior Art
All aluminum canoes made today are constructed of two pieces, a left side and right side which are connected by rivets to a keel. In addition, aluminum canoes usually employ several structural ribs to improve strength and rigidity. The net results are that a standard 16 foot canoe may have 500 rivets located below the waterline, each of which is a potential leak. Furthermore, a large number of rivets can weaken the material because of the large number of holes formed for the rivets. Also, the holes can act as stress risers further aggravating problems of metal fatigue and shortening use life of the canoe. Finally, rivet heads below the waterline can be broken by underwater obstructions and create drag.
Accordingly, what is desired is a canoe that has a unitary smooth body with no rivets or other penetrating structural components below the waterline. In addition, the canoe should be constructed from aluminum because of its light weight, corrosion resistance, and resistance to degradation caused by ultraviolet light from the sun.
What is also most desirable in canoes is an asymmetrical hull design wherein the bow is narrower than usual in order to reduce drag associated with the entry of the hull into water.
Finally, a canoe design and construction should minimize thermal conduction through the floor and reduce the noise often associated with aluminum canoes.
Present canoe designs and methods of construction are inadequate and do not provide the strength, the long life, the low drag and the light weight needed for modern canoes.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a method of producing a watercraft for passengers having a unitary body comprises the steps of forming a unitary watercraft body from a single unitary sheet of metal; fabricating a rigid floor adaptable for attachment to the watercraft body; and attaching the floor to the watercraft body. In other aspects another step is included which comprises placing the sheet from the forming step into a replica female mold prior to the attaching step, and the attaching step includes the steps of rigidly holding a floor member above the bottom interior surface of the watercraft body at a predetermined fixed height; and injecting an expanding foam through openings in the floor member into the space between the interior surface of the watercraft and the lower surface of the floor member that will adhere to the respective surfaces when it cures. The placing step includes the steps of placing the formed body in a mold substantially conforming to the exterior surface of the body for rigidly supporting the body in position; and removing excess material from the body to conform it to substantially the desired dimensions of the watercraft. The invention also directed to the additional steps of placing the formed body in a first mold substantially conforming to the exterior surface of the body for supporting the body in position therein; removing excess material from the body to substantially conform it to the desired dimensions of the watercraft; removing the body from the first mold; and placing the trimmed body in a second mold conforming to the replica exterior surface of the body of the watercraft for rigidly supporting the body in position therein.
In other aspects, preferably the forming step includes the steps of providing a mold in a desired shape corresponding substantially to the body of the watercraft; forcing the mold into the sheet of metal to cause the sheet to imprint the shape of the mold onto the sheet; forcing the perimeter portion of the sheet onto the mold; and removing the formed sheet from the mold. The forming step also includes the steps of cutting a pair of oppositely disposed notches in the ends of the sheet each of which is aligned with the centerline of the sheet; providing a mold in a desired shape of a body of a watercraft onto which the sheet is to be formed; grasping each end of the sheet substantially along the entire length of the end portion adjacent each notch; forcibly pivoting each of the grasped ends in an arc about an axis along the centerline of the sheet to force the perimeter portion of the sheet onto the mold; releasing the grasped ends of the sheet; and removing the sheet from the mold. The forcibly pivoting step includes the step of forcibly pulling outwardly on the grasped ends of the sheet in a direction in line with the sheet centerline to place the sheet under tension for further forcing of the sheet onto the mold.
In another aspect of the present invention there is provided the steps of providing a mold in a desired shape corresponding substantially to the body of the watercraft; cutting a pair of oppositely disposed notches in the ends of the sheet each of which is aligned with the centerline of the sheet; grasping each end of the sheet substantially along the entire length of the end portion adjacent each notch; forcing the mold into the sheet of metal to cause the sheet to imprint the shape of the mold onto the sheet; forcibly pivoting each of the grasped ends in an arc about an axis along the centerline of the sheet to force the perimeter portion of the sheet onto the mold; releasing the grasped ends of the sheet; removing the sheet from the mold; providing a replica female mold; rigidly holding a floor member above the bottom interior surface of the watercraft body at a predetermined fixed height; injecting an expanding urethane foam through openings in the floor member into the space between the interior surface of the watercraft body and the lower surface of the floor member that will adhere to the respective surfaces when it curves; releasing the floor member after the foam injected in step M has cured; removing the watercraft from the female mold; and joining together respective notched end portions at each end of the body.
In another aspect of the present invention, a passenger watercraft is provided and includes a unitary sheet metal body including a lower portion having an interior surface and opposite end portions; a rigid floor member extending from one said end portion to the other said end portion and having an upper surface and a lower surface; and means for attaching said floor member to said body above said lower surface. Other features include means for attaching including a substantially rigid material, the interior surface of the body and lower surface of the floor member defining a cavity, the cavity being substantially filled by the material, the material adhering to each of the interior and lower surfaces to attach the floor member to the body and provide substantial support throughout the floor and minimize deflection of the lower portion of the sheet metal body. The rigid material is chemically expanded structural flotation, urethane foam and the sheet metal is a sheet of deep-formable aluminum. The floor member includes a plurality of spaced ports for the injection of the means for attaching therethrough, a plurality of closure members respectively capping each of the ports after injection of the means for attaching has been terminated. The sheet metal body is smooth and continuous throughout a portion below a waterline of the watercraft to minimize drag and to maximize resistance to leaks and is in the form of a canoe having symmetrical and opposed sides and having assymmetrical end portions. The rigid floor member is substantially planar and the means for attaching is a rigid structural flotation foam material which adheres to each of the floor member lower surface and the interior surface of the lower end portion of the metal body to form a unitized structural beam throughout the extent of the floor member and the lower end portion of the metal body.